Comparative tyrosine degradation in Vibrio cholerae strains. The strain ATCC 14035 as a prokaryotic melanogenic model of homogentisate-releasing cell

Sánchez-Amat, Antonio; Ruzafa, Carolina; Solano, Francisco

doi:10.1016/s0305-0491(98)00028-5

Cited by 28 publications

(31 citation statements)

References 23 publications

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“…In the sequenced strains Philadelphia, Paris, and Lens, hmgA is designated lpg1285, lpp1248, and lpl1248 (14,16). HmgA, whether prokaryotic or eukaryotic, degrades HGA to 4-maleyl-acetoacetate and, therefore, in its absence HGA more readily oxidizes to benzoquinoneacetic acid, which then polymerizes to form pyomelanin (4,33,64,92,94). As an indication of its relatedness to like enzymes, L. pneumophila HmgA showed 65% similarity to Pseudomonas putida HmgA (4).…”

Section: Resultsmentioning

confidence: 99%

The Secreted Pyomelanin Pigment of Legionella pneumophila Confers Ferric Reductase Activity

2007

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The virulence of Legionella pneumophila is dependent upon its capacity to acquire iron. To identify genes involved in expression of its siderophore, we screened a mutagenized population of L. pneumophila for strains that were no longer able to rescue the growth of a ferrous transport mutant. However, an unusual mutant was obtained that displayed a strong inhibitory effect on the feoB mutant. Due to an insertion in hmgA that encodes homogentisate 1,2-dioxygenase, the mutant secreted increased levels of pyomelanin, the L. pneumophila pigment that is derived from secreted homogentisic acid (HGA). Thus, we hypothesized that L. pneumophilasecreted HGA-melanin has intrinsic ferric reductase activity, converting Fe 3؉ to Fe 2؉ , but that hyperpigmentation results in excessive reduction of iron that can, in the case of the feoB mutant, be inhibitory to growth. In support of this hypothesis, we demonstrated, for the first time, that wild-type L. pneumophila secretes ferric reductase activity. Moreover, whereas the hyperpigmented mutant had increased secreted activity, an lly mutant specifically impaired for pigment production lacked the activity. Compatible with the nature of HGA-melanins, the secreted ferric reductase activity was positively influenced by the amount of tyrosine in the growth medium, resistant to protease, acid precipitable, and heterogeneous in size. Together, these data represent the first demonstration of pyomelanin-mediated ferric reduction by a pathogenic bacterium.Legionella pneumophila, an occupant of natural and humanmade aquatic environments, is also the principal agent of Legionnaires' disease, a serious form of pneumonia that especially afflicts immunocompromised individuals (18,37,41). In water habitats, this gram-negative bacterium survives free, in biofilms, and as an intracellular parasite of protozoa (2, 62, 65); in the lung, it replicates in alveolar macrophages (67,93,95). Among the processes that promote L. pneumophila growth in both the environment and the mammalian host are Lsp type II protein secretion, Dot/Icm type IVB protein secretion, and the Lvh type IVA protein secretion system (8,19,27,57,84,105). Other notable surface features of L. pneumophila include flagella, type IV pili, the major outer membrane protein porin, the Hsp60 chaperonin, and the Mip peptidylproline isomerase (9,26,39,46,49,66,88,99,108). In addition to exporting proteins and enzymes onto its surface or into the extracellular milieu and/or host cells, L. pneumophila also secretes a siderophore (legiobactin) that promotes iron uptake (3). Iron acquisition has long been regarded as a key aspect of L. pneumophila growth, intracellular infection, and virulence (12,17,82). Besides legiobactin, we have uncovered both FeoB ferrous iron transport, which is critical for bacterial growth in host cells and the lung, as well as the ccm, frgA, hbp, iraAB, and tat genes, which also promote L. pneumophila growth under low-iron conditions (20,47,68,73,81,86,87,106,107). The discovery of legiobactin has drawn further attention...

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Section: Resultsmentioning

confidence: 99%

The Secreted Pyomelanin Pigment of Legionella pneumophila Confers Ferric Reductase Activity

2007

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“…It is probable that the red pigment of C. psychrerythraea, which is responsible for the name of this organism (70), is a pyomelanin, or alkapton, formed from spontaneous dimerization and oxidation of homogentisic acid. Interestingly, C. psychrerythraea thus appears to be a prokaryotic model of the disease alkaptonuria (71), where patients also lack the enzyme homogentisate dioxygenase.…”

Section: Discussionmentioning

confidence: 99%

Structure of Phenylalanine Hydroxylase from Colwellia psychrerythraea 34H, a Monomeric Cold Active Enzyme with Local Flexibility around the Active Site and High Overall Stability

Leiros

Pey

Innselset

et al. 2007

Journal of Biological Chemistry

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The characteristic of cold-adapted enzymes, high catalytic efficiency at low temperatures, is often associated with low thermostability and high flexibility. In this context, we analyzed the catalytic properties and solved the crystal structure of phenylalanine hydroxylase from the psychrophilic bacterium Colwellia psychrerythraea 34H (CpPAH). . Normal mode and COREX analysis also detect these and other areas with high flexibility. Greater mobility around the active site and disrupted hydrogen bonding abilities for the cofactor appear to represent cold-adaptive properties that do not markedly affect the thermostability of CpPAH.

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“…More recently, this type of melanin has also been characterized in Burkholderia cenocepacia, a gram-negative opportunistic pathogen that can survive within phagocytic cells, and the synthesis of this melanin is a defense mechanism against the host cell [149], similarly to some pathogenic fungus, such as Aspergillus fumigates [124]. Moreover, pyomelanin from HGA has some relevance since the situation is comparable to the human alkaptonuria [147,148], a rare disease due to mutations in the homogentisate dioxygenase human gene. This inactive enzyme leads to deposits of pyomelanin in the cartilage.…”

Section: Bacterial Melaninmentioning

confidence: 99%

“…As stated above, this type of melanin is also formed in some fungi. Shewanella colweliana [145] and Vibrio cholerae [146][147][148] synthesize pyomelanin in response to specific physiological conditions that are stressful to the bacteria. Under those conditions, there is accumulation of homogentisic acid because of the low activity of homogentisate dioxygenase.…”

Section: Bacterial Melaninmentioning

confidence: 99%

Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes

Solano

2014

New Journal of Science

429

431

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This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a doubleedged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.

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Comparative tyrosine degradation in Vibrio cholerae strains. The strain ATCC 14035 as a prokaryotic melanogenic model of homogentisate-releasing cell

Cited by 28 publications

References 23 publications

The Secreted Pyomelanin Pigment of Legionella pneumophila Confers Ferric Reductase Activity

The Secreted Pyomelanin Pigment of Legionella pneumophila Confers Ferric Reductase Activity

Structure of Phenylalanine Hydroxylase from Colwellia psychrerythraea 34H, a Monomeric Cold Active Enzyme with Local Flexibility around the Active Site and High Overall Stability

Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes

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